EEG Brain Rhythms During Resting-State Wakefulness and Sleep in Elderly Expert Meditators

Abstract

Meditation practice has been shown to impact resting-state EEG activity in expert meditators, but its benefits on sleep, which is particularly affected with age, are poorly understood. Our aim was to better understand the effects of long-term meditation practice on resting-state EEG and sleep in older adults. Twenty-seven elderly expert meditators (mean age ± SD: 70.7 ± 5.0 years) were compared to meditation-naive controls (69.3 ± 3.8 years) for sleep questionnaires (n = 135), polysomnography (n = 47) and resting-state EEG (n = 73). Sleep microstructure (slow waves and spindles) and EEG features (power, Kolmogorov complexity and permutation entropy (PE)) during resting-state, NREM, and REM sleep were compared between groups. Correlations were tested between the metrics that differed between the two groups and the level of meditation expertise within the meditator group. At rest, expert meditators exhibited lower delta power and higher delta PE than controls. Self-reported sleep quality did not differ between groups, but expert meditators slept longer, had reduced %N1, and higher %N2. During NREM sleep, they exhibited reduced delta power, increased alpha power, and greater theta PE. During REM sleep, they tended to show greater theta power. Finally, the composite score of meditation expertise was negatively associated with %N1, and tended to be positively associated with %N2 and REM sleep theta power. Overall, these results suggest that expert meditators showed more preserved brain activity at rest and sleep architecture, and exhibited EEG features suggesting higher cognitive states during NREM sleep. Clinical Trial Information: Name: Study in Cognitively Intact Seniors Aiming to Assess the Effects of Meditation Training (Age-Well). Registration: EudraCT: 2016-002441-36; IDRCB: 2016-A01767-44; ClinicalTrials.gov Identifier: NCT02977819. (https://clinicaltrials.gov/ct2/show/NCT02977819?term=Age-Well&draw=2&rank=1).

Keywords: EEG; N; REM sleep; ageing; meditation; wakefulness.